Enhanced Sensitivity of a Hydrogen Sulfide Sensor Based on Surface Acoustic Waves at Room Temperature

Abstract

In this contribution, a new surface acoustic wave (SAW)-based sensor was proposed for sensing hydrogen sulfide (H2S) at room temperature (30 °C), which was composed of a phase discrimination circuit, a SAW-sensing device patterned with delay line, and a triethanolamine (TEA) coating along the SAW propagation path of the sensing device. The TEA was chosen as the sensitive interface for H2S sensing, owing to the high adsorption efficiency by van der Waals’ interactions and hydrogen bonds with H2S molecules at room temperature. The adsorption in TEA towards H2S modulates the SAW propagation, and the change in the corresponding phase was converted into voltage signal proportional to H2S concentration was collected as the sensor signal. A SAW delay line patterned on Y-cut quartz substrate with Al metallization was developed photographically, and lower insertion and excellent temperature stability were achieved thanks to the single-phase unidirectional transducers (SPUDTs) and lower cross-sensitivity of the piezoelectric substrate. The synthesized TEA by the reaction of ethylene oxide and ammonia was dropped into the SAW propagation path of the developed SAW device to build the H2S sensor. The developed SAW sensor was characterized by being collecting into the phase discrimination circuit. The gas experimental results appear that fast response (7 s at 4 ppm H2S), high sensitivity (0.152 mV/ppm) and lower detection limit (0.15 ppm) were achieved at room temperature. It means the proposed SAW sensor will be promising for H2S sensing.

ZnO Metal Oxide Semiconductor in Surface Acoustic Wave Sensors: A Review

“…Among the gases most targeted for detection using ZnO- and ZnO-based materials in SAW sensors, as shown in Table 2 , are hydrogen [ 45 , 112 ], acetone [ 100 , 165 ], hydrogen sulfide [ 82 , 166 ], ethanol [ 44 , 100 ], and ammonia [ 80 , 150 ]. Of these, most RT SAW sensors were made for hydrogen, ammonia and ethanol, for which sensitivities between 11 and 0.005 Hz/ppm were obtained ( Table 2 ) [ 1 ].…”

Acoustofluidic separation enables early diagnosis of traumatic brain injury based on circulating exosomes

“…By generating surface acoustic waves (SAWs) with tilted-angle interdigital transducer (IDT) pairs, a tilted-angle standing wave field is generated and can separate particles based on differences in size and density [42][43][44] . In our previous study, an acoustofluidic device was used to successfully isolate exosomes from whole blood at a high yield while maintaining the morphology and molecular content of isolated exosomes 39,45 .…”

ZnO-Al2O3 nanocomposite as a sensitive layer for high performance surface acoustic wave H2S gas sensor with enhanced elastic loading effect

“…Recently, surface acoustic wave (SAW) technique has been used in the H2S gas sensing because of its advantages of low power consumption, low operation temperature, excellent stability, sensitivity and wireless control capabilities [10][11][12][13].…”

“…Galipeau et al [15] reported a SAW H2S sensor using WO3 as the sensitive layer, and it achieved a response of ~600 Hz to 0.25 ppm H2S. These studies [10][11][12][13][14][15][16][17] have all concluded that the key sensing mechanism of the sensors are the changes of the weight (mass loading effect) and electrical conductivity (electrical loading effect) of the sensing layers when the sensor is exposed to H2S gas. However, as we know, there is another important sensing mechanism, i.e., the changes of elastic modulus (elastic loading effect), which has seldomly been investigated or explored for H2S gas sensing using the SAW technique.…”